2007 DB9 Fuel Pumps
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Joined: Feb 2026
Posts: 6
From: Omaha, NE
Rep Power: 0
I'm wondering if I'd be better off getting a good aftermarket regulator valve/filter and just pulling out everything from the pump output to the tank bulkhead. It would require a bit more engineering on my end, but might serve me better long term. I've had symptoms as early as 2021 (mainly just emission system codes, and nothing that impacted performance until 2024).
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Registered User
Joined: Aug 2017
Posts: 273
From: Alpharetta, GA
Rep Power: 70
it's possible the previous owner had fuel system issues and a dealer already installed the fuel line kit. Now that you've got the tank open you can check everything over. Be thankful you have a Volante. I still have scars (physical and emotional) from my experience with the coupe.
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Joined: Feb 2026
Posts: 6
From: Omaha, NE
Rep Power: 0
Well, we figured it out.
Turns out the pumps (and lines in the tank) were all fine after all. Thankfully, pumps are impossible to source right now, otherwise I'd have spent a bunch more money than I needed to.
The culprit? Relay 15. $19 in stock at my local AutoZone. Hidden in the passenger footwell in the CEM. The relay was actuating, however there was about 250-400 ohms of resistance across the shut contacts, which was causing erratic signals to the FPDMs, sporadic stutters in the pump running, and all sorts of weird codes about bank 2 lean or fuel pressure low....nothing that pointed directly to the relay. After we swapped it out, the car started as if I had driven it yesterday (after sitting not able to start for nearly a year). No stuttering, no lump at idle - just smooth operation.
I appreciate the insight and expertise from everyone who helped along the way. I learned a lot about the system through the digging around in the car and the tank and pouring over endless wiring diagrams. Hopefully this will help someone in the future who is experiencing similar symptoms as I was - check relay 15! it takes 10 seconds to check this $19 relay and could save you years and thousands of dollars chasing something that's hiding in an unsuspecting part.
Turns out the pumps (and lines in the tank) were all fine after all. Thankfully, pumps are impossible to source right now, otherwise I'd have spent a bunch more money than I needed to.
The culprit? Relay 15. $19 in stock at my local AutoZone. Hidden in the passenger footwell in the CEM. The relay was actuating, however there was about 250-400 ohms of resistance across the shut contacts, which was causing erratic signals to the FPDMs, sporadic stutters in the pump running, and all sorts of weird codes about bank 2 lean or fuel pressure low....nothing that pointed directly to the relay. After we swapped it out, the car started as if I had driven it yesterday (after sitting not able to start for nearly a year). No stuttering, no lump at idle - just smooth operation.
I appreciate the insight and expertise from everyone who helped along the way. I learned a lot about the system through the digging around in the car and the tank and pouring over endless wiring diagrams. Hopefully this will help someone in the future who is experiencing similar symptoms as I was - check relay 15! it takes 10 seconds to check this $19 relay and could save you years and thousands of dollars chasing something that's hiding in an unsuspecting part.
Registered User
Joined: Feb 2019
Posts: 609
From: Northern VA
Rep Power: 34
Well, we figured it out.
Turns out the pumps (and lines in the tank) were all fine after all. Thankfully, pumps are impossible to source right now, otherwise I'd have spent a bunch more money than I needed to.
The culprit? Relay 15. $19 in stock at my local AutoZone. Hidden in the passenger footwell in the CEM. The relay was actuating, however there was about 250-400 ohms of resistance across the shut contacts, which was causing erratic signals to the FPDMs, sporadic stutters in the pump running, and all sorts of weird codes about bank 2 lean or fuel pressure low....nothing that pointed directly to the relay. After we swapped it out, the car started as if I had driven it yesterday (after sitting not able to start for nearly a year). No stuttering, no lump at idle - just smooth operation.
I appreciate the insight and expertise from everyone who helped along the way. I learned a lot about the system through the digging around in the car and the tank and pouring over endless wiring diagrams. Hopefully this will help someone in the future who is experiencing similar symptoms as I was - check relay 15! it takes 10 seconds to check this $19 relay and could save you years and thousands of dollars chasing something that's hiding in an unsuspecting part.
Turns out the pumps (and lines in the tank) were all fine after all. Thankfully, pumps are impossible to source right now, otherwise I'd have spent a bunch more money than I needed to.
The culprit? Relay 15. $19 in stock at my local AutoZone. Hidden in the passenger footwell in the CEM. The relay was actuating, however there was about 250-400 ohms of resistance across the shut contacts, which was causing erratic signals to the FPDMs, sporadic stutters in the pump running, and all sorts of weird codes about bank 2 lean or fuel pressure low....nothing that pointed directly to the relay. After we swapped it out, the car started as if I had driven it yesterday (after sitting not able to start for nearly a year). No stuttering, no lump at idle - just smooth operation.
I appreciate the insight and expertise from everyone who helped along the way. I learned a lot about the system through the digging around in the car and the tank and pouring over endless wiring diagrams. Hopefully this will help someone in the future who is experiencing similar symptoms as I was - check relay 15! it takes 10 seconds to check this $19 relay and could save you years and thousands of dollars chasing something that's hiding in an unsuspecting part.
Lately I have been liberally applying dielectric grease to all connections to reduce the amount of corrosion. Learned this the hard way on a mini cooper with similar issues... High ohmic loss at the relay due to corrosion.
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